Japanese company Naniwa was founded in Osaka in 1941. Its main activity is the production of various sharpening products for cutting tools. Today, Naniwa has an excellent reputation as a manufacturer of high-quality classic water stones for sharpening and is the recognized world leader in the production of magnesia-bonded aluminum oxide abrasives. In addition to premium artificial abrasives, Naniwa also produces a variety of profile accessories such as stone holders and stands, sharpening stones, sharpening stones dressing stones, etc.
Naniwa sharpening stones are synthetic abrasives and are manufactured using the most advanced technology, with a variety of bonding agents. Due to the unique manufacturing technology, these stones are characterized by high performance and due to their structure can be used for any steel with a hardness of up to 68 Rockwell units. Compared to natural sharpening stones, they have a more homogeneous composition and produce much more suspension. The grain is constantly renewed during the sharpening process, resulting in a high performance gain.
Naniwa produces two of today’s most sought-after synthetic water stone series, Naniwa Professional Stones and Naniwa Super Stones, as well as several other specialized series.
Naniwa Professional Stones
The most popular series is the Naniwa Professional Stones or Naniwa Chosera series for the Japanese market. The size of the stone is 210x70x20. This is a series of high quality stones designed for professionals who are professionally engaged in sharpening cutting tools. This series is categorized as professional stones because of its very high productivity. It is this parameter is emphasized by the creators of the Professional Stone series.
The stones are made with a magnesia bond. It is a magnesia cement that hardens in air by mixing caustic magnesite and magnesium chloride solution. Magnesia-bonded abrasive has low mechanical strength and hygroscopicity, so it should be stored in a dry room. Moisture leads to cracking of the bars and their further unsuitability for sharpening work. One of the main features of this bond is its high density with a uniform consistency of finely dispersed abrasive particles. This gives the bars the highest work efficiency among water stones. The most popular stones from this series are:
1. Naniwa Professional Stone #600 series water stone is designed for deburring and rough sharpening.
2. Naniwa Professional Stone #1000 series water stone is for basic sharpening.
3. Naniwa Professional Stone #3000 series water stone is for basic sharpening.
4. Naniwa Professional Stone #5000 series water stone is for pre-finish sharpening.
There are also other stones in the Naniwa Professional series from 400 to 10000. The grit of all these stones is given in the Japanese JIS system.
Naniwa Super Stones
The Naniwa Sharpening Stones or Naniwa Super Stones series for the Japanese market, has the same sharpening bar sizes as the Naniwa Professional Stone series. It is designed for sharpening the widest range of cutting tools, both in terms of purpose and material of manufacture. Compared to the Naniwa Professional Stone Series, this series has a smaller capacity, but the stones are slower to produce. This series is made with an organic bond, with Bakelitized resin as a base. The stones themselves are more durable than Naniwa Professional, but remove metal less productively.
Naniwa also produces other series of stones: Naniwa Specialty Stones are multi-purpose stones for specialized tools. Naniwa (Traditional Stones) – designed to work specifically with Japanese knives and other cutting tools made with traditional technologies such as Shiro Gami (white paper), Ki Gami (yellow paper), Ao Gami (blue paper), etc.; Naniwa Coarse Stone – coarse stones for coarse deburring work, etc.
Naniwa stones, regardless of the series, do not require immersion in water, and a spray gun is required to work with them. These abrasives are sensitive to prolonged exposure to water. They should be dried well and stored in a dry place. If the storage rules are not followed, the stones may crack and lose their abrasive properties. They should not be left wet in the cold, frozen water can destroy the stone. These abrasives may have white salt streaks (efflorescence), which is normal. They should be allowed to air dry when finished. Do not try to speed up the drying process by exposing the bars to heat; they must dry evenly to retain their qualities. Stones that are completely dry can be put away for storage.
Naniwa abrasives need regular dressing to help reduce uneven wear. Stones should be dressed on the thickest possible glass with their own slurry, without silicon carbide powder.
Special stands can be used to make working with these stones more comfortable. They help to prevent the water stone from slipping and lift the stone off the work surface, which is especially useful when sharpening knives.